Source code for MDAnalysis.auxiliary.XVG
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# Please cite your use of MDAnalysis in published work:
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# R. J. Gowers, M. Linke, J. Barnoud, T. J. E. Reddy, M. N. Melo, S. L. Seyler,
# D. L. Dotson, J. Domanski, S. Buchoux, I. M. Kenney, and O. Beckstein.
# MDAnalysis: A Python package for the rapid analysis of molecular dynamics
# simulations. In S. Benthall and S. Rostrup editors, Proceedings of the 15th
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# doi: 10.25080/majora-629e541a-00e
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# N. Michaud-Agrawal, E. J. Denning, T. B. Woolf, and O. Beckstein.
# MDAnalysis: A Toolkit for the Analysis of Molecular Dynamics Simulations.
# J. Comput. Chem. 32 (2011), 2319--2327, doi:10.1002/jcc.21787
#
"""
XVG auxiliary reader --- :mod:`MDAnalysis.auxiliary.XVG`
========================================================
xvg files are produced by Gromacs during simulation or analysis, formatted
for plotting data with Grace.
Data is column-formatted; time/data selection is enabled by providing column
indices.
Note
----
By default, the time of each step is assumed to be stored in the first column,
in units of ps.
.. autoclass:: XVGStep
:members:
XVG Readers
-----------
The default :class:`XVGReader` reads and stores the full contents of the .xvg
file on initialisation, while a second reader (:class:`XVGFileReader`) that
reads steps one at a time as required is also provided for when a lower memory
footprint is desired.
Note
----
Data is assumed to be time-ordered.
Multiple datasets, separated in the .xvg file by '&', are currently not
supported (the readers will stop at the first line starting '&').
.. autoclass:: XVGReader
:members:
.. autoclass:: XVGFileReader
:members:
.. autofunction:: uncomment
"""
import numbers
import os
import numpy as np
from . import base
from ..lib.util import anyopen
[docs]def uncomment(lines):
"""Remove comments from lines in an .xvg file
Parameters
----------
lines : list of str
Lines as directly read from .xvg file
Yields
------
str
The next non-comment line, with any trailing comments removed
"""
for line in lines:
stripped_line = line.strip()
# ignore blank lines
if not stripped_line:
continue
# '@' must be at the beginning of a line to be a grace instruction
if stripped_line[0] == "@":
continue
# '#' can be anywhere in the line, everything after is a comment
comment_position = stripped_line.find("#")
if comment_position > 0 and stripped_line[:comment_position]:
yield stripped_line[:comment_position]
elif comment_position < 0 and stripped_line:
yield stripped_line
# if comment_position == 0, then the line is empty
[docs]class XVGStep(base.AuxStep):
"""AuxStep class for .xvg file format.
Extends the base AuxStep class to allow selection of time and
data-of-interest fields (by column index) from the full set of data read
each step.
Parameters
----------
time_selector : int | None, optional
Index of column in .xvg file storing time, assumed to be in ps. Default
value is 0 (i.e. first column).
data_selector : list of int | None, optional
List of indices of columns in .xvg file containing data of interest to
be stored in ``data``. Default value is ``None``.
**kwargs
Other AuxStep options.
See Also
--------
:class:`~MDAnalysis.auxiliary.base.AuxStep`
"""
def __init__(self, time_selector=0, data_selector=None, **kwargs):
super(XVGStep, self).__init__(
time_selector=time_selector, data_selector=data_selector, **kwargs
)
def _select_time(self, key):
if key is None:
# here so that None is a valid value; just return
return
if isinstance(key, numbers.Integral):
return self._select_data(key)
else:
raise ValueError("Time selector must be single index")
def _select_data(self, key):
if key is None:
# here so that None is a valid value; just return
return
if isinstance(key, numbers.Integral):
try:
return self._data[key]
except IndexError:
errmsg = (
f"{key} not a valid index for data with "
f"{len(self._data)} columns"
)
raise ValueError(errmsg) from None
else:
return np.array([self._select_data(i) for i in key])
[docs]class XVGReader(base.AuxReader):
"""Auxiliary reader to read data from an .xvg file.
Default reader for .xvg files. All data from the file will be read and
stored on initialisation.
Parameters
----------
filename : str
Location of the file containing the auxiliary data.
**kwargs
Other AuxReader options.
See Also
--------
:class:`~MDAnalysis.auxiliary.base.AuxReader`
Note
----
The file is assumed to be of a size such that reading and storing the full
contents is practical.
"""
format = "XVG"
_Auxstep = XVGStep
def __init__(self, filename, **kwargs):
self._auxdata = os.path.abspath(filename)
with anyopen(filename) as xvg_file:
lines = xvg_file.readlines()
auxdata_values = []
# remove comments before storing
for i, line in enumerate(uncomment(lines)):
if line.lstrip()[0] == "&":
# multiple data sets not supported; stop at end of first set
break
auxdata_values.append([float(val) for val in line.split()])
# check the number of columns is consistent
if len(auxdata_values[i]) != len(auxdata_values[0]):
raise ValueError(
"Step {0} has {1} columns instead of "
"{2}".format(i, auxdata_values[i], auxdata_values[0])
)
self._auxdata_values = np.array(auxdata_values)
self._n_steps = len(self._auxdata_values)
super(XVGReader, self).__init__(**kwargs)
def _memory_usage(self):
return self._auxdata_values.nbytes
def _read_next_step(self):
"""Read next auxiliary step and update ``auxstep``.
Returns
-------
AuxStep object
Updated with the data for the new step.
Raises
------
StopIteration
When end of auxiliary data set is reached.
"""
auxstep = self.auxstep
new_step = self.step + 1
if new_step < self.n_steps:
auxstep._data = self._auxdata_values[new_step]
auxstep.step = new_step
return auxstep
else:
self.rewind()
raise StopIteration
def _go_to_step(self, i):
"""Move to and read i-th auxiliary step.
Parameters
----------
i: int
Step number (0-indexed) to move to
Returns
-------
:class:`XVGStep`
Raises
------
ValueError
If step index not in valid range.
"""
if i >= self.n_steps or i < 0:
raise ValueError(
"Step index {0} is not valid for auxiliary "
"(num. steps {1})".format(i, self.n_steps)
)
self.auxstep.step = i - 1
self.next()
return self.auxstep
[docs] def read_all_times(self):
"""Get NumPy array of time at each step.
Returns
-------
NumPy array of float
Time at each step.
"""
return self._auxdata_values[:, self.time_selector]
[docs]class XVGFileReader(base.AuxFileReader):
"""Auxiliary reader to read (one step at a time) from an .xvg file.
An alternative XVG reader which reads each step from the .xvg file as
needed (rather than reading and storing all from the start), for a lower
memory footprint.
Parameters
----------
filename : str
Location of the file containing the auxiliary data.
**kwargs
Other AuxReader options.
See Also
--------
:class:`~MDAnalysis.auxiliary.base.AuxFileReader`
Note
----
The default reader for .xvg files is :class:`XVGReader`.
"""
format = "XVG-F"
_Auxstep = XVGStep
def __init__(self, filename, **kwargs):
super(XVGFileReader, self).__init__(filename, **kwargs)
def _read_next_step(self):
"""Read next recorded step in xvg file and update ``auxstep``.
Returns
-------
AuxStep object
Updated with the data for the new step.
Raises
------
StopIteration
When end of file or end of first data set is reached.
"""
line = next(self.auxfile)
while True:
if not line or (line.strip() and line.strip()[0] == "&"):
# at end of file or end of first set of data (multiple sets
# currently not supported)
self.rewind()
raise StopIteration
# uncomment the line
for uncommented in uncomment([line]):
# line has data in it; add to auxstep + return
auxstep = self.auxstep
auxstep.step = self.step + 1
auxstep._data = [float(i) for i in uncommented.split()]
# see if we've set n_cols yet...
try:
auxstep._n_cols
except AttributeError:
# haven't set n_cols yet; set now
auxstep._n_cols = len(auxstep._data)
if len(auxstep._data) != auxstep._n_cols:
raise ValueError(
f"Step {self.step} has "
f"{len(auxstep._data)} columns instead "
f"of {auxstep._n_cols}"
)
return auxstep
# line is comment only - move to next
line = next(self.auxfile)
def _count_n_steps(self):
"""Iterate through all steps to count total number.
Returns
-------
int
Total number of steps
"""
if not self.constant_dt:
# check if we've already iterated through to build _times list
try:
return len(self._times)
except AttributeError:
# might as well build _times now, since we'll need to iterate
# through anyway
self._times = self.read_all_times()
return len(self.read_all_times())
else:
# don't need _times; iterate here instead
self._restart()
count = 0
for step in self:
count = count + 1
return count
[docs] def read_all_times(self):
"""Iterate through all steps to build times list.
Returns
-------
NumPy array of float
Time of each step
"""
self._restart()
times = []
for step in self:
times.append(self.time)
return np.array(times)